Field Guide
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Brown Rat
Rattus norvegicus
Not yet photographed by the community
Introduced in 18th century; highly adaptable; swims well.
Species Profile
Not listed (non-native invasive species); managed as a pest in the UK
- Lifespan
- 2–3 years in the wild; up to 4 years in captivity
- Size & Weight
- Body 20–25 cm, tail 19–23 cm; 200–500 g
- Habitat
- Highly adaptable to urban, agricultural, and industrial environments, particularly buildings, sewers, and areas near human food sources.
- UK Distribution
- Found throughout the UK, including urban centres, farms, and rural areas. Resident year-round with populations reinforced by seasonal migrations.
- Diet
- Omnivorous; feeds on grains, seeds, fruits, nuts, insects, and meat; highly opportunistic scavenger exploiting human food waste.
- Predators
- Owls (Barn, Tawny), foxes, stoats, weasels, domestic cats, and birds of prey.
- Mating Season
- Year-round, peaking March to October
- Breeding
- Females produce 6–12 litters annually with 6–12 pups per litter; gestation period 21–23 days; pups weaned at 3–4 weeks.
- Behaviour
- Highly social, living in colonies with hierarchical structures; primarily nocturnal and excellent swimmers. Brown rats are neophobic (wary of new objects) but highly intelligent and capable of problem-solving.
- •Originally native to northern China and Mongolia, brown rats were introduced to Europe via shipping routes and reached the UK around 1728.
- •Brown rats possess excellent senses of smell, hearing, and taste but relatively poor vision; they navigate using their whiskers (vibrissae).
- •A single female can produce up to 2,000 offspring per year under ideal conditions, making population control challenging.
- •Brown rats can tread water for up to 3 days and hold their breath for several minutes, allowing them to emerge from toilets and drains.
- •In the UK, brown rats cause an estimated £1 billion in annual damage through contamination, disease transmission, and structural damage to buildings.
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